1. Field of the Invention
The present invention generally relates to a vehicle guidance method for a navigation system, and particularly relates to a vehicle guidance method for a navigation system when no road information around an input destination is detected.
2. Description of the Related Art
In a conventional navigation system for providing travelling guidance for a vehicle so that a driver of the vehicle can easily arrive at a desired destination, the vehicle position is detected and map data around the vehicle position is read from a CD-ROM or the like. A map image is displayed on a display screen on which a vehicle position mark (car mark) is displayed at a predetermined position. In accordance with changes in the current vehicle position caused by movement of the vehicle, the car mark on the screen is moved or the map is scrolled while the car mark is fixed at a predetermined position, such as the center of the image, thus instantly providing map information around the vehicle position.
The navigation system includes a route guidance function for setting a guidance route from a departure point to a destination, for displaying the guidance route on the map, and for giving guidance at intersections. When the departure point and the destination are input, a guidance route controller of the navigation system automatically determines the optimal guidance route and sequentially stores nodes (longitude, latitude) that form the guidance route in a guidance route memory. During travell, node strings stored in the guidance route memory are searched for the guidance route in a map display area on the screen. The guidance route is displayed so as to be discriminated from other roads. When the vehicle is within a predetermined distance from an approaching intersection, an intersection guidance image (an enlarged image of the intersection and an arrow indicating the direction of travel at the intersection) is displayed. The driver of the vehicle may thereby determine which road to take or which direction to take at the intersection.
When a facility in an unmapped area (a rural area in which only highways such as expressways are entered since not all data is mapped) is input as a destination in the conventional navigation system, a guidance route may not be searched for or guidance may be terminated at an inappropriate location due to a lack of road information around the destination. The navigation system fails to provide a user with information on the guidance route to the desired destination, causing inconvenience for the user.
Accordingly, it is an object of the present invention to provide a navigation system for providing, by organizing correspondence between facilities and freeway exits near the facilities into a database, an appropriate freeway exit as a temporary destination even when a facility in an unmapped area is input as a destination, and for providing route guidance to the destination.
It is another object of the present invention to provide a navigation system for displaying a direction from a temporary destination (freeway exit) to a destination (facility) as an arrow or a line and for displaying a linear distance from the temporary destination to the destination, thus guiding a vehicle to the destination as a user desires.
To this end, according to the present invention, when no road information around an input destination is detected, a freeway exit near the destination is obtained as a temporary destination. The vehicle is guided to the temporary destination along a guidance route.
Correspondence between a facility, a location thereof, and a freeway exit may be organized into a database. When data is input to specify the facility as the destination, a freeway exit corresponding to the facility is obtained from the database.
When the vehicle arrives at the temporary destination, a display screen sequentially displays a line or an arrow indicating the direction from a vehicle position to the destination and a linear distance from the vehicle position to the destination. Therefore, the vehicle may be guided to the destination.
Specifically, even when a facility in an unmapped area is input as a destination, normal route guidance is provided until the vehicle arrives at the freeway exit near the facility. Subsequently, the navigation system guides the vehicle by displaying the arrow or the line and the distance to the destination, thus guiding the vehicle to the user""s desired destination.